1. Field of the Invention
This invention relates to establishing data communication between client nodes over a network and more particularly to establishing deterministic network performance between client nodes which use normally nondeterministic (legacy) bus types.
2. Description of the Related Art
Modern system applications increasingly require the capabilities of a high-speed data bus network that not only has plentiful bandwidth, but can also provide a deterministic quality of service in providing inter-node communication. Some of the most popular shared bandwidth high-speed data buses such as Ethernet and Fibre Channel (Arbitrated Loop), etc., though providing much-improved bandwidths over earlier buses, do not inherently provide time-deterministic performance as part of their protocol.
Attempts to achieve time-deterministic data delivery over such networks have given rise to techniques currently coming to market such as introducing one or several (as necessary) time-deterministic buffer switches between all nodes of a network (e.g., Next Generation System's Copperhead™ deterministic Ethernet crossbar switch), and creating deterministic point-to-point multi-hop connections between pairs of communicating client nodes routed through one or more crossbar switches, while retaining the original data bus protocol (e.g., Ethernet) on all links of the network. Such an approach can involve considerable expense, as with the Copperhead™ Ethernet switches being priced at about $10,000 each. A network of ten such switches with 8 ports each (totaling $100,000) are required to provide connectivity between 60 nodes. All that expense is incurred trying to provide determinism to the Ethernet protocol.
An approach is needed for allowing multiple high speed buses, whether inherently non-deterministic in nature or not, to achieve deterministic messaging capability and to co-exist and reside on a single primary vehicle network type. The present subject invention provides time-deterministic capability between nodes supported by otherwise non-deterministic network types in a simpler and lower cost manner than other techniques currently coming to market.
The subject invention provides deterministic messaging capability between nodes which interface with and communicate over normally non-deterministic legacy data buses (e.g., Ethernet, Universal Serial Bus (USB) or Fibre Channel Arbitrated Loop). This is accomplished by merging the time-deterministic capabilities of a shared bandwidth, multi-node, deterministic bus (viz., IEEE-1394b) with dedicated (un-contended) point-to-point connections for the first and last leg connections to the otherwise non-deterministic legacy node interfaces.
Some software methods have been developed for partitioning such functions across an arbitrary network and connecting them together with a communications protocol. One such method and standard is known as the Scalable Coherent Interface, and is defined by the open system standard IEEE-1596.